5 Answers
5

Take certain supplements like vitamin b-complex, ginseng and fish oils.

Leave your study location, go for a walk and then come back. Changing your environment helps switching "off" your brain and then when you come back you're ready to go.

Power nap - set an alarm for 20 minutes so you definitely wake up. Once you go beyond 30 minutes you get into deep sleep and it becomes very difficult to wake up until an hour later (sleep cycle is about 90 minutes).

Long-term

Get enough sleep each night.

Regular exercise - this one is the biggest. Exercising 2-3 times a week will help you stay energized.

Eat healthy - less processed food, more fruits, and more smaller meals throughout the day.

Try BEACH method. BEACH is an acronym with which I came up to easily remember 5 words representing simple activities that can everyone do to relax and recover. All of them have something to do with water.

Beverage → Drink a glass of water (or some other cold non-alcoholic
beverage)

Exercise → Do some stretching, move with your body, you can
imagine you are swimming and move with your hands properly.

Atmosphere → Use pictures, music and other media to support the
imagination that your on the beach or sea.

Contrast → Everything you
do and imagine during the relaxation break should be as much
different from your work as possible.